Monday, July 20, 2009

Super-Sipping Data Centers

Data centers are known for their energy hog reputations. Doomers' Armageddon energy-depletion scenarios envision data centers, known for their finicky dependence on generous air-conditioning, sparking out because a lack of power, or the grid giving out, thus cutting off air-conditioning and fizzling out the Internet like a B&W TV shutting off. A Saratoga-based startup has developed a splendid memory chip, which they claim can replace data centers' hard drives, and use only 5% of the power of the drives. If true, you won't believe the electric bill savings (link).

And not any kind of flash memory. Sandforce's chip is particularly designed to allow multi-level cell (MLC) flash to take on corporate jobs. MLC flash can hold two or more bits in a memory cell and is the cheapest kind on the market. It's the stuff you find in cameras and MP3 players.

"Storage will be free if they [corporate owners] take the total cost of ownership into account," said CEO Alex Navqi. "Over five years, they amount of power saved will pay for itself in five years."

A traditional datacenter with 240 high-end drives holding approximately 73 gigabytes each could be replaced by one with 9 Sandforce-enabled drives, he said. The energy cost for storage in the traditional datacenter would cost $50,000 over five years. The Sandforce-enabled one would have a cumulative energy bill of $250.

Put another way, total storage costs per gigabyte, including energy, would come to $3.16 for hard drives and $1.43 per gigabyte. The math assumes fewer flash drives would be needed because of better input/output, he argued. On a straight comparison, a high-end 73-gigabyte hard disk would need $211 in power-including air conditioning power-over five years. A 73-gigabyte flash drive would get by on $52 of power.

[...]

The key to Sandforce's processors is that they effectively mask the technological shortcomings of MLC. Like all flash memory, MLC essentially stores data by brute force. A flash memory cell consists of a sealed silicon dioxide, or glass, tube, similar to the flask inside of a thermos. To write data to a flash cell, an electrical charge is applied that leaves a set number of electrons inside the sealed tube. To erase data, another charge is applied. Flash engineers describe the process as violent.

The problem is that the tube is getting thinner and smaller with each turn of the Moore's Law crank. Flash chips made on the 20 nanometer process, coming in a few years, may only accommodate about 20 electrons, said Navqi. Escaping electrons in turn leads to errors and data corruption.

"Every time you hit the oxide, you damage it," he said. As a result, a conventional flash drive (without the company's chips) would have to be replaced every 30 days because of the number of data rewrites.

The company's DuraClass technology gets around the problem by only rewriting the cells that require an update. An entry in a Social Security file, hypothetically, might contain 100,000 bytes. An update to the data might only affect 100 bytes. Traditional flash drives would rewrite the whole entry. DuraClass organizes the data and functionality of the chip so that only 100 bytes get impacted. In all, a DuraClass-enabled drive could last over five years with equal or better performance when it comes to data reliability under ordinary corporate pounding.